A proximate principle of feebly alkaloidal power, prepared from pepper, and occurring also in other plants of the Nat. Ord. Piperaceae.

Characters. - Colourless, or pale yellowish, shining, four-sided prisms, permanent in the air, odourless, and almost tasteless when first put in the mouth, but on prolonged contact producing a sharp and biting sensation. When heated to about 128° C. (about 262° F.), piperine melts, yielding a clear, yellowish liquid, which, on cooling, congeals to a resinous mass. It has a neutral reaction.

Solubility. - It is almost insoluble in water, but soluble in 30 parts of alcohol at 15° C. (59° F.), in 1 part of boiling alcohol, and but slightly soluble in ether.

Reactions. - When heated on platinum foil, it takes fire and is consumed without residue. Concentrated sulphuric acid dissolves piperine with a dark, blood-red colour, which disappears on dilution with water. When treated with cold nitric acid, piperine turns rapidly greenish-yellow, orange, and red, and gradually dissolves with a reddish colour. On adding to this solution an excess of solution of potassa, the colour is at first pale yellow, but on boiling it deepens to blood-red, while, at the same time, vapours of an alkaline reaction and of a peculiar odour (piperidine) are given off.

Dose. - 1 to 10 grains.

Action and Uses. - Pepper is a stimulant stomachic. It is used chiefly as a condiment, but has been employed in the treatment of haemorrhoids, and, on account of its stimulating action on mucous membranes, as a substitute for cubebs in the treatment of gonorrhoea. The action and uses of piperine are similar to those of pepper.